A number of defects, diseases and pathological conditions in a variety of areas of medicine would benefit from the development of noninvasive treatments utilizing improved gene delivery vehicles and systems that allow the safe, efficient and sustained production of gene products to an affected tissue or organ site. In particular, improved cell-mediated gene delivery vehicles and methods would find wide use in ameliorating non-fatal, yet debilitating, pathologies of the musculoskeletal system, such as arthritis and joint disease (e.g., ligament, meniscus and cartilage); the bone, such as segmental bone defects and non-unions; and the genitourinary system, such as urinary incontinence and bladder conditions.
Although synovial cells have been used to deliver potentially therapeutic agents into the joint, the expression of such agents has declined over time, thereby causing these agents generally to become undetectable after about four to six weeks. (G. Bandara et al., 1993, Proc. Natl. Acad. Sci. USA, 90(22):10764-10768; C. H. Evans and P. D. Robbins, 1995, Ann. Med., 27(5):543-546; C. H. Evans and P. D. Robbins, 1994, J. Rheum., 21(5):779-782). This decline in expression over time may be ameliorated by the use of cell mediated gene delivery employing a myogenic cell type that becomes post-mitotic with differentiation, in accordance with the present invention.
Segmental bone defects and non-unions are relatively common problems facing all orthopedic surgeons. Osteogenic proteins, e.g., bone morphogenic protein-2, BMP-2), can promote bone healing in segmental bone defects. However, a large quantity of the human recombinant protein is needed to enhance bone healing potential. Moreover, current modes of delivering such quantities of protein, i.e., a biological allograft or a synthetic carrier, are hampered by limited availability, possible disease transmission and the need for further research and investigation.
Cell mediated gene therapy in the bone defect would allow a sustained expression of osteogenic proteins, further enhance bone healing, and offer a solution to the problems surrounding current methods of bone protein delivery. Thus, in accordance with the present invention, the utilization of muscle-derived cells, e.g., myoblasts, as cellular gene delivery vehicles to correct or improve a bone defect, provides an important step in establishing a less invasive treatment for non-unions and segmental bone defects.
Ex vivo gene therapy and myoblast transplantation are two closely related methods which require in vitro cell isolation and culture. Ex vivo techniques involve muscle biopsy and myogenic cell isolation (T. A. Rando et al., 1994, J. Cell Biol., 125:1275-1287; Z. Qu et al., 1998, J. Cell Biol., 142(5):1257-1267). The isolated muscle-derived cells are transduced in vitro with the desired gene carrying vector. The satellite cells are then reinjected into skeletal muscle, fuse to form post-mitotic myotubes and myofibers, and begin growth factor production. This technique is feasible with adenoviral, retroviral, and herpes simplex viral vectors.
The following are examples of orthopaedic applications for muscle based gene therapy and tissue engineering related to the practice of the present invention:
Muscle Injury and Repair
Muscle injuries comprise a large percentage of recreational and competitive athletic injuries. Muscle injuries may result from both direct (e.g., contusions, lacerations) and indirect (e.g., strains, ischemia and neurological injuries) trauma. Upon injury, satellite cells are released and activated in order to differentiate into myotubes and myofibers, thereby promoting muscle healing. However, this reparative process is usually incomplete and accompanied by a fibrous reaction producing scar tissue. This scar tissue limits the muscle's potential for functional recovery (T. Hurme et al., 1991; Med. Sci. Sports Exerc., 23:801-810; T. Hurme et al., 1992, Med. Sci. Sports Exerc., 24:197-205).
Investigations in animals have identified possible clinical applications for muscle-based tissue engineering to treat muscle injuries (W. E. Garrett et al., 1984; J. Hand Surgery (Am). 9A:683-692; W. E. Garrett et al., 1990, Med. Sci. Sports Exerc., 22:436-443). Injured skeletal muscle releases numerous growth factors acting in autocrine and paracrine fashion to modulate muscle healing. These proteins activate satellite cells to proliferate and differentiate into myofibers (T. Hurme, 1992, Med. Sci. Sports Exerc., 24:197-205; R. Bischoff, 1994, “The satellite cell and muscle regeneration”. Myology. 2nd Edition. New York, McGraw-Hill, Inc, pp. 97-118; H. S. Allamedine et al., 1989; Muscle Nerve, 12:544-555; E. Schultz et al., 1985, Muscle Nerve, 8:217; E. Schultz, 1989, Med. Sci. Sports Exerc., 21:181).
Muscle-based tissue engineering offers exciting potential therapies for muscle disorders. A large number of recreational and professional athletic injuries involve skeletal muscle (Garrett et al., 1990, Med. Sci. Sports Exerc., 22:436-443). Therapies to improve functional recovery and shorten rehabilitation may both optimize performance and minimize morbidity. Further research is ongoing to refine these muscle-based tissue engineering applications. The results of such investigations may provide revolutionary treatments for these common muscle injuries. The present invention provides new and exciting treatments for muscle repair following muscle-based injuries, particularly for application in clinical settings.
Bone Healing
Multiple surgical specialties, including orthopaedic, plastic, and maxillofacial, are concerned with bone healing augmentation. Physicians in these disciplines rely on bone augmentation techniques to improve healing of fracture non-unions, oncologic and traumatic bone defect reconstructions, joint and spine fusions, and artificial implant stabilizations. Unfortunately, current techniques of autograft, allograft, and electrical stimulation are often suboptimal. Therefore, tissue engineering approaches toward bone formation have immense implications.
Intramuscular bone formation is a poorly understood phenomenon. It can be present in the clinically pathologic states of heterotopic ossification, myositis ossificans, fibrodysplasia ossificans progressiva and osteosarcoma. Radiation therapy and the anti-inflammatory drug, indomethicin, can suppress myositis ossificans. However, neither the mechanism of formation nor suppression of ectopic bone is clearly understood. A growing family of bone morphogenetic proteins (BMPs), members of the transforming growth factor β (TGF-β) superfamily, are recognized as being capable of stimulating intramuscular bone. Human BMP-2 in recombinant form (rhBMP-2) and BMP-encoding cDNA contained in a plasmid construct induce bone formation when injected into skeletal muscle (E. A. Wang et al., 1990, Proc. Natl. Acad. Sci. USA, 87:2220-2224; J. Fang et al, 1996, Proc. Natl. Acad. Sci. USA, 93:5753-5758). Current applications focus on injecting rhBMP-2 directly into non-unions and bone defects. However, muscle-based tissue engineering has enormous promise in the arena of bone healing and may shed light on the physiologic mechanism of ectopic bone formation.
Intraarticular Disorders
Degenerative and traumatic joint disorders are encountered frequently as our population becomes more active and lives longer. These disorders include arthritis of various etiologies, ligament disruptions, meniscal tears, and osteochondral injuries. Currently, the clinician's tools consist primarily of surgical procedures aimed at biomechanically altering the joint, such as anterior cruciate ligament (ACL) reconstructions, total knee replacement, meniscal repair or excision, cartilage debridement, etc. Tissue engineering applied to these intraarticular disease states theoretically offers a more biologic and less disruptive reparative process.
Both direct (I. Nita et al., 1996, Arthritis Rheum., 39:820-828) and ex vivo (G. Bandara et al., 1993, Proc. Natl. Acad. Sci. USA, 90:10764-10768) gene therapy approaches to arthritis models have been reported. The synovial cell-mediated ex vivo approach, while offering advantages of ex vivo gene transfer such as the safety of in vitro genetic manipulation and precise cell selection, is hindered by a decline of gene expression after 5-6 weeks (Bandara et al., 1993, Ibid.). Due to its ability to form post-mitotic myotubes and myofibers, the satellite cell offers the theoretical advantages of longer term and more abundant protein production.
Muscle cell-mediated ex vivo gene delivery to numerous intraarticular structures is possible. Intraarticular injection of primary myoblasts, transduced by adenovirus carrying the β-galactosidase marker gene, results in gene delivery to many intraarticular structures (C. S. Day et al., 1997, J. Orthop. Res., 15:227-234). Tissues expressing β-galactosidase at 5 days after injection in the rabbit knee include the synovial lining, meniscal surface, and cruciate ligament (Ibid.). In contrast, injection of transduced synovial cells results in β-galactosidase expression only in the synovium (Ibid.). Likewise, injection of transduced immortalized myoblasts results in gene delivery to various intraarticular structures, including the synovial lining and patellar ligament surface. However, the purified immortalized myoblasts fused more readily and resulted in more de novo intraarticular myofibers than the primary myoblasts. This illustrates the importance of obtaining a pure population of myogenic cells, void of the fibroblast and adipocyte contamination often seen in primary myoblasts.
Muscle cell-mediated ex vivo approaches are predicated on myoblast fusion to form myofibers, the plurinuclear protein-producing factories. Intraarticular injection of transduced immortalized myoblasts into a severe combined immune deficient (SCID) mouse results in myotube formation and transgene expression in multiple structures at 35 days. Therefore, intraarticular gene expression (for at least 35 days) resulting from muscle cell-mediated tissue engineering is feasible in animal models. Based on this data, a muscle cell-mediated gene transfer approach may deliver genes to improve the healing of several intraarticular structures specifically to the ACL and meniscus.
The ACL is the second most frequently injured knee ligament. Unfortunately, the ACL has a low healing capacity, possibly secondary to its encompassing synovial sheath or the surrounding synovial fluid. Because complete tears of the ACL are incapable of spontaneous healing, current treatment options are limited to surgical reconstruction using autograft or allograft. The replacement graft, often either patella ligament or hamstring tendon in origin, undergoes ligamentization with eventual collagen remodeling (S. P. Arnosczky et al., 1982, Am. J. Sports Med., 10:90-95). Therefore, augmentation of this ligamentization process using growth factors to affect fibroblast behavior is envisioned by the practice of the methods described herein. In vivo data suggests that platelet-derived growth factor (PDGF), transforming growth factor-β (TGF-β), and epidermal growth factor (EGF) promote ligament healing (N. A. Conti et al., 1993, Trans. Orthop. Res. Soc., 18:60). Transient, low levels of these growth factors resulting from their direct injection into the injured ligament are unlikely to produce a significant response. Therefore, an efficient delivery mechanism is essential to the development of a clinically applicable therapy. Muscle cell-mediated ex vivo gene therapy according to the teachings herein offers the potential to achieve persistent local gene expression and subsequent growth factor delivery to the ACL.
With more specific regard to the knee, the knee meniscus plays a critical role in maintaining normal knee biomechanics. Primary functions of the meniscus include load transmission, shock absorption, joint lubrication, and tibiofemoral stabilization in the ACL deficient knee. The historical treatment of menisectomy for meniscal tears has been replaced by meniscal repair when tears involve the meniscus' peripheral, vascular third. Growth factors, including platelet-derived growth factor (PDGF), are capable of enhancing meniscal healing (K. P. Spindler et al., 1995, J. Orthop. Res., 13(2):201-207). However, needed for both the practitioner and the patient are better methods and procedures to deliver such needed factors to the meniscus to provide healing and repair.
Urologic Applications
Urinary incontinence is a devastating medical and social condition. The incidence of urinary incontinence is increasing in the United States due to an aging population. As of January 1997, the National Institute of Diabetes and Digestive and Kidney Disease has launched a public health campaign to address the fact that there are over eleven million women and four million men in the United States who have urinary incontinence problems. Approximately half of the fifteen million people with incontinence have stress urinary incontinence; however, less than half of the afflicted people are seeking help and receiving the treatments which are available (Agency for Health Care Policy and Research, AHCPR, 1992 and 1996).
Presently, the estimated annual cost for treating people with urinary incontinence is over $16 billion in the United States. Most of this money is spent on management measures, such as adult diapers and pads, rather than on treatment. Since most of the invasive and surgical treatment for urinary incontinence involves the treatment of stress urinary incontinence, the cost for managing stress urinary incontinence is estimated at $9 billion dollars per year in the United States (AHCPR 1996).
In evaluating an individual with incontinence, three of the most common types and causes of incontinence can be identified: a) urge incontinence, b) stress incontinence, or c) overflow incontinence (M. B. Chancellor and J. G. Blaivas, 1996, Atlas of Urodynamics, Williams and Wilkins, Philadelphia, Pa.).
Stress incontinence is the involuntary loss of urine during coughing, sneezing, laughing, or other physical activities which increase abdominal pressure. This condition may be confirmed by observing urine loss coincident with an increase in abdominal pressure, in the absence of a bladder contraction or an overdistended bladder. The condition of stress incontinence may be classified as either urethral hypermobility or intrinsic sphincter deficiency. In urethral hypermobility, the bladder neck and urethra descend during cough or strain on urodynamic and the urethra opens with visible urinary leakage (leak point pressure between 60-120 cm H2O). In intrinsic sphincter deficiency, the bladder neck opens during bladder filling without bladder contraction. Visible urinary leakage is seen with minimal or no stress. There is variable bladder neck and urethral descent, often none at all, and the leak point pressure is low (<60 cm H2O). (J. G. Blaivas, 1985, Urol. Clin. N. Amer., 12:215-224; D. R. Staskin et al., 1985, Urol. Clin. N. Amer., 12:271-278).
Urge incontinence is defined as the involuntary loss of urine associated with an abrupt and strong desire to void. Although involuntary bladder contractions can be associated with neurologic disorders, they can also occur in individuals who appear to be neurologically normal (P. Abrams et al., 1987, Neurol. & Urodynam., 7:403-427). Common neurologic disorders associated with urge incontinence are stroke, diabetes, and multiple sclerosis (E. J. McGuire et al, 1981, J. Urol., 126:205-209). Urge incontinence is caused by involuntary detrusor contractions that can also be due to bladder inflammation and impaired detrusor contractility where the bladder does not empty completely.
Overflow incontinence is characterized by the loss of urine associated with overdistension of the bladder. Overflow incontinence may be due to impaired bladder contractility or to bladder outlet obstruction leading to overdistension and overflow. The bladder may be underactive secondarily to neurologic conditions such as diabetes or spinal cord injury, or following radical pelvic surgery.
Another common and serious cause of urinary incontinence (urge and overflow type) is impaired bladder contractility. This is an increasingly common condition in the geriatric population and in patients with neurological diseases, especially diabetes mellitus (N. M. Resnick et al., 1989, New Engl. J. Med., 320:1-7; M. B. Chancellor and J. G. Blaivas, 1996, Atlas of Urodynamics, Williams and Wilkins, Philadelphia, Pa.). With inadequate contractility, the bladder cannot empty its content of urine; this causes not only incontinence, but also urinary tract infection and renal insufficiency. Presently, clinicians are very limited in their ability to treat impaired detrusor contractility. There are no effective medications to improve detrusor contractility. Although urecholine can slightly increase intravesical pressure, it has not been shown in controlled studies to aid effective bladder emptying (A. Wein et al., 1980, J. Urol., 123:302). The most common treatment is to circumvent the problem with intermittent or indwelling catheterization.
There are a number of treatment modalities for stress urinary incontinence. The most commonly practiced current treatments for stress incontinence include the following: absorbent products; indwelling catheterization; pessary, i.e., vaginal ring placed to support the bladder neck; and medication (Agency for Health Care Policy and Research. Public Health Service: Urinary Incontinence Guideline Panel. Urinary Incontinence in Adults: Clinical Practice Guideline. AHCPR Pub. No. 92-0038. Rockville, Md. U.S. Department of Health and Human Services, March 1992; M. B. Chancellor, Evaluation and Outcome. In: The Health of Women With Physical Disabilities: Setting a Research Agenda for the 90's. Eds. Krotoski D. M., Nosek, M., Turk, M., Brooks Publishing Company, Baltimore, Md., Chapter 24, 309-332, 1996). With specific regard to medication, there are several drugs approved for the treatment of urge incontinence. However, there are no drugs approved or effective for stress urinary incontinence.
Exercise is another treatment modality for stress urinary incontinence. For example, Kegel exercise is a common and popular method to treat stress incontinence. The exercise can help half of the people who can do it four times daily for 3-6 months. Although 50% of patients report some improvement with Kegel exercise, the cure rate for incontinence following Kegel exercise is only 5 percent. In addition, most patients stop the exercise and drop out from the protocol because of the very long time and daily discipline required.
Another treatment method for urinary incontinence is the urethral plug. This is a new, inexpensive disposable cork-like plug for women with stress incontinence. A new plug should be used after each micturition, with an estimated daily cost of about $15-20. The estimated annual disposable cost is over $5,000. The plug is associated with over 20% urinary tract infection and, unfortunately, does not cure incontinence.
Biofeedback and functional electrical stimulation using a vaginal probe are also used to treat urge and stress urinary incontinence. However, these methods are time-consuming and expensive and the results are only moderately better than Kegel exercise. Surgeries, such as laparoscopic or open abdominal bladder neck suspensions; transvaginal approach abdominal bladder neck suspensions; artificial urinary sphincter (expensive complex surgical procedure with 40% reversion rate) are also used to treat stress urinary incontinence.
Other treatments include urethra injection procedures with exogenous injectable materials such as Teflon, collagen, and autologous fat. Each of these injectables has its disadvantages. More specifically, there are significant reservations among those in the medical community concerning the use of Teflon. Complications of Teflon injection include granuloma, diverticulum, cysts, and urethral polyp formation. Of greatest concern is the migration (via the lymphatic and vascular systems) of Teflon particles to distant locations, resulting in fever and pneumonitis.
Collagen injections generally employ bovine collagen, which is expensive and is often reabsorbed, resulting in the need for repeated injections. A further disadvantage of collagen is that about 5% of patients are allergic to bovine source collagen and develop antibodies.
Autologous fat grafting as an injectable bulking agent has a significant drawback in that most of the injected fat is resorbed. In addition, the extent and duration of the survival of an autologous fat graft remains controversial. An inflammatory reaction generally occurs at the site of implant. Complications from fat grafting include fat resorption, nodules and tissue asymmetry.
In view of the above-mentioned limitations and complications of treating urinary incontinence and bladder contractility, new and effective modalities in this area are needed in the art. In accordance with the present invention, muscle cell injection therapy using uniquely engineered muscle-derived cells is provided as an improved and novel means for treating and curing various types of incontinence, particularly, stress urinary incontinence and for the enhancement of urinary continence. As but one advantage, muscle-derived cell injection can preferably be autologous, so that there will minimal or no allergic reactions, unlike the aforementioned use of collagen. Also, unlike collagen, myogenic cells such as blasts are not absorbed; thus, they can provide a better improvement and cure rate.
Myoblasts, the precursors of muscle fibers, are mononucleated muscle cells which differ in many ways from other types of cells. Myoblasts naturally fuse to form post-mitotic multinucleated myotubes which result in the long-term expression and delivery of bioactive proteins (T. A. Partridge and K. E. Davies, 1995, Brit. Med. Bulletin, 51:123-137; J. Dhawan et al., 1992, Science, 254: 1509-1512; A. D. Grinnell, 1994, In: Myology. Ed 2, Ed. Engel AG and Armstrong CF, McGraw-Hill, Inc, 303-304; S. Jiao and J. A. Wolff, 1992, Brain Research, 575:143-147; H. Vandenburgh, 1996, Human Gene Therapy, 7:2195-2200). Myoblasts have been used for gene delivery to muscle for muscle-related diseases, such as Duchenne muscular dystrophy (E. Gussoni et al., 1992, Nature, 356:435-438; J. Huard et al., 1992, Muscle & Nerve, 15:550-560; G. Karpati et al., 1993, Ann. Neurol., 34:8-17; J. P. Tremblay et al., 1993, Cell Transplantation, 2:99-112), as well as for non-muscle-related diseases, e.g., gene delivery of human adenosine deaminase for the adenosine deaminase deficiency syndrome (C. M. Lynch et al., 1992, Proc. Natl. Acad. Sci. USA, 89:1138-1142); gene transfer of human proinsulin for diabetes mellitus (G. D. Simonson et al., 1996, Human Gene Therapy, 7:71-78); gene transfer for expression of tyrosine hydroxylase for Parkinson's disease (S. Jiao et al., 1993, Nature, 362:450); transfer and expression of Factor IX for hemophilia B (Y. Dai et al., 1995, Proc. Natl. Acad. Sci. USA, 89:10892), delivery of human growth hormone for growth retardation (J. Dhawan et al., 1992, Science, 254:1509-1512).
The use of myoblasts to treat muscle degeneration, to repair tissue damage or treat disease is disclosed in U.S. Pat. Nos. 5,130,141 and 5,538,722. Also, myoblast transplantation has been employed for the repair of myocardial dysfunction (S. W. Robinson et al., 1995, Cell Transplantation, 5:77-91; C. E. Murry et al., 1996, J. Clin. Invest., 98:2512-2523; S. Gojo et al., 1996, Cell Transplantation, 5:581-584; A. Zibaitis et al., 1994, Transplantation Proceedings, 26:3294).
Nitric oxide (NO) has been recognized as a important transmitter in genitourinary tract function. NO mediates smooth muscle relaxation and is also the key to achieving erection. Recently, constitutive and inducible nitric oxide synthase (NOS or iNOS) have been demonstrated in the urothelium, bladder and urethra wall. A deficiency in urinary NO in patients having interstitial cystitis bladder inflammation (M. A. Wheeler et al., 1997, J. Urol., 158(6):2045-2050; S. D. Smith et al., 1997, J. Urol., 158(3 Pt 1):703-708). Moreover, patients with interstitial cystitis had improvement in urinary symptoms and increased urinary NO production when treated with oral L-Arginine (M. A. Wheeler et al., 1997, J. Urol., 158(6):2045-2050). Recent evidence has shown that urethral smooth muscle relaxation is mediated by NO release and that NO also mediates prostate smooth muscle relaxation (H. Kakizaki et al., 1997, Am. J. Phys., 272:R1647-1656; A. L. Burnett, 1995, Urology, 45:1071-1083; M. Takeda et al., 1995, Urology, 45:440-446; W. Bloch et al., 1997, Prostate, 33:1-8).